Why did a number of groups pushing for reform emerge during the late 1800s and early 1900s

A rich history of social movements shaped progressive thought throughout the 19th and 20th centuries. Historian Sidney Milks characterizes the accomplishments of the original Progressive Era as "momentous reconstructions of politics," a description that equally applies to the numerous social movements that aimed to better align America's political and social order with its ideals of liberty, equality, and opportunity for all.